But what is memory? Many of us think memory is like a photograph or a recording somewhere in our brain. If only we could find that one place then we could remember what we wanted to remember. Research has shown us that memory is much more complicated than this. Memory is also different from perception because memory deals with events in our past.
Our memory process involves three steps. The first step is called the encoding step because it involves the intake of information and possibly creates what is called a memory trace. This is followed by the storage step. Our brain needs to place the information somewhere so that it can be maintained over time. When we want to recall a piece of information, the brain is involved in the last step called retrieval because we attempt to access the memory traces scattered throughout our brain.
This can sound like a daunting task. Our brain has about 100 billion brain cells. These cells work by being interconnected with many other cells. As they pass on information to these other cells, the number of pathways is astronomical. Amid all this interconnectedness, there is no one place where memory exists. Memory, we have discovered, is scattered throughout many different sites in our brain.
For example, say your brain encodes and stores a memory about a lunch you had with a friend. The memory of who your friend is goes one place for storage, the location of your lunch goes somewhere else. What you ate and the time of day are both stored in different locations in your brain. During the lunch, sights, sounds, smells, tastes are all distributed in separate parts of your brain. To retrieve this information, your hippocampus has to rummage through all these different areas of you brain to put together the memory of "your lunch." Where are these other places?
Although the hippocampus is considered the memory control center, many other parts of the brain are also involved in memory. Memories are distributed among such places as the cerebellum, cerebral cortex, amygdala and striatum. These different parts of the brain have different functions regarding your memory but they also affect each other.
To make things even more complicated, scientists now talk about different kinds of memory. You are probably familiar with the terms "long term" and "short term" memory. Short term memory is often referred to as our "working memory" because it generally lasts about thirty seconds and deals with about seven pieces of information at a time. If we repetitively concentrate on these items in short term memory, it is more likely they will eventually be transferred to long term memory storage.
Long term memory is where we permanently store information. Theoretically, it has an unlimited capacity. Psychologists have found that there are different types of long term memory. Each of these types has a different purpose.
One type is called procedural memory. This type of memory deals with "how" we do things and our skills involving motor patterns. Another is called declarative memory. We use this type of memory when we remember information or knowledge about our world. Examples of declarative memory would be remembering someone's name or when to attend a class you signed up for. Procedural memory would be used for remembering how to play the trombone, fix a table lamp or perform specific movements in aikido.
Declarative memory (remembering information) can be subdivided into episodic and semantic memory. Episodic memory remembers things that have a specific anchor in our past. We know where information came from and maybe the circumstances surrounding its origin. On the other hand, semantic memory is also about knowledge and information but we don't know where the information came from or when we might have learned it.
In 1987 a psychologist by the name of Daniel Schacter at Harvard, identified two other types of memory: explicit memory and implicit memory. He had been studying different types of memory tasks and found that some tasks were very active in recalling information. The person using this type of memory knows and is aware of what is being remembered. He called this explicit memory.
Implicit memory is a bit more difficult to explain. Essentially this memory type also recalls past experiences or information but during this recall, we are not consciously aware of these previous experiences. In a sense, procedural memory is a form of implicit memory. People continually use implicit, procedural memory. You know how to drive your care without having to consciously think about how to do it or remember when and how you learned to do it.
With all these different memory types in the brain and locations where memory is stored, it is now easy to see that our memories are not stored as in a video camera. When we want or need to retrieve a memory, the brain begins searching for these pieces and tries to put them together into a meaningful whole.
You have probably had the experience of trying to remember something like a person's name. You recognize the face, where you've seen the person before, any emotion attached to it, but still have to say, "the name is on the tip of my tongue." When this happens, your brain is searching for that missing piece but is unable to find it. We keep trying to come up with the name and often find that it pops into our head when we have given up trying to remember it.
Our brain, then, constructs memories of past information like trying to find the pieces of a puzzle. Sometimes, when our brain cannot find the missing piece, it will get another piece that is similar but not accurate. Many of us have talked about a childhood event with a parent only to have them say, "but that's not how it happened at all." This frustrates us because we "know" that our memory of the event is the way it really happened.
This is why it is so easy to get into an active argument with someone about what "really" happened in the past that both people were a part of. Each person is absolutely convinced he or she is correct and the other person has to be wrong.
As if this were not bad enough. Elizabeth Loftus, a highly respected psychologist who specializes in memory research, has found that our memories can be manipulated by how our external cues are arranged. In a famous experiment she showed a video clip of a car lightly hitting another car. After watching the clip half the people were asked to estimate how fast the car had been moving when it "smashed" into the other car. The other half of the group were asked how fast the car had been moving when it "bumped" the other car.
The people in the "smashed" group guessed that the car was traveling much faster than the speed estimated by the second "bumped" group. Merely by asking the question with a single different word – smashed vs. bumped – was enough to influence the memories of people in the first group.
Because your memory is an active process, it uses a variety of strategies to retrieve information. It can and often will fill in the missing elements without your permission. As memory research continues, we will probably find even more surprises awaiting us.